A data network generally consists of a network of multiple independent and clustered nodes connected by point-to-point links. Each node may be an intermediate node, such as a switch/switch element, a repeater, and a router, or an end-node within the network, such as a host system and an I/O unit (e.g., data servers, storage subsystems and network devices). Message data may be transmitted from source to destination, often through intermediate nodes.
Existing interconnect transport mechanisms, such as PCI (Peripheral Component Interconnect) buses as described in the “PCI Local Bus Specification, Revision 2.1” set forth by the PCI Special Interest Group (SIG) on Jun. 1, 1995, may be utilized to deliver message data to and from I/O devices, namely storage subsystems and network devices. However, PCI buses utilize a shared memory-mapped bus architecture that includes one or more shared I/O buses to deliver message data to and from storage subsystems and network devices. Shared I/O buses can pose serious performance limitations due to the bus arbitration required among storage and network peripherals as well as posing reliability, flexibility and scalability issues when additional storage and network peripherals are required. As a result, existing interconnect technologies have failed to keep pace with computer evolution and the increased demands generated and burden imposed on server clusters, application processing, and enterprise computing created by the rapid growth of the Internet.
Emerging solutions to the shortcomings of existing PCI bus architecture are InfiniBand™ and its predecessor, Next Generation I/O (NGIO) which have been developed by Intel Corporation to provide a standards-based I/O platform that uses a switched fabric and separate I/O channels instead of a shared memory-mapped bus architecture for reliable data transfers between end-nodes, as set forth in the “Next Generation Input/Output (NGIO) Specification,” NGIO Forum on Jul. 20, 1999 and the “InfiniBan™ Architecture Specification,” the InfiniBand™ Trade Association scheduled for publication in late October 2000. Using NGIO/InfiniBand™, a host system may communicate with one or more remote systems using a Virtual Interface (VI) architecture in compliance with the “Virtual Interface (VI) Architecture Specification, Version 1.0,” as set forth by Compaq Corp., Intel Corp., and Microsoft Corp., on Dec. 16, 1997. NGIO/InfiniBand™ and VI hardware and software may often be used to support data transfers between two memory regions, typically on different systems over one or more designated channels. Each host system using a VI Architecture may contain work queues (WQ) formed in pairs including inbound and outbound queues in which requests, in the form of descriptors, are posted to describe data movement operation and location of data to be moved for processing and/or transportation via a data network. Each host system may serve as a source (initiator) system which initiates a message data transfer (message send operation) or a target system of a message passing operation (message receive operation). Requests for work (data movement operations such as message send/receive operations and remote direct memory access “RDMA” read/write operations) may be posted to work queues associated with a given network interface card. One or more channels between communication devices at a host system or between multiple host systems connected together directly or via a data network may be created and managed so that requested operations can be performed.
However, in this architecture it is necessary for each part of the fabric to have an understanding of the nodes that are present therein. In the current architecture, this procedure is very time consuming and requires a lot of bandwidth. Accordingly, there is a need to provide a method for mapping the nodes of each subnet in the fabric in a fashion which is quick and requires a minimum of bandwidth.